Mortar barrel



June 23,' 1970 2 Sheets-Sheet 1 Filed April 12, 1968 Junezs, 1970 synoNNER 3,516,326

MORTAR BARRELA Filed April 12, 1968 2 Sheets-Sheet 2 /A/nswmf United States Patent U.S. Cl. 89-14 10 Claims ABSTRACT OF THE DISCLOSURE Either the interior of the barrel of a mortar or the exterior of a mortar projectile is provided with longitudinally extending ribs which guide the projectile as it is discharged from the barrel or during the phase at which combustion gases are blown out of the barrel.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to mortars and projectiles therefor.

Description of the prior art Since a mortar is a muzzle loader, it is necessary to leave a small space between the projectile and the wall of the barrel in order that the captive air may escape. In current practice the diameter of the projectile is slightly smaller than that of the barrel, `which results in a lack of symmetry on the firing of the projectile. This causes irregular movements of the insuciently guided projectile, which leave the muzzle in an inclined position. These disadvantages are still further increased by the blast of combustion gases against the incline projectile during the very rst portion of its trajectory.

It is an object of the present invention to obviate these disadvantages and for this purpose the invention relates to improvements having the effect of providing effective guiding of the projectile in the course of its movement in the barrel or during the phase at which combustion gases are blown out of the barrel.

SUMMARY According to one aspect of the invention there is provided a muzzle-loading mortar barrel characterised in that on its inner face it has elongated projections along at least one component of a direction parallel to the axis of the -barrel and extending at least over part of its length, said projections dening a circular gauge passage along the barrel.

For the purposes of the present specification the expression circular gauge dimension of an element is to be understood as meaning the circle of minimum diameter circumscribed around said element, and by circular gauge passage is to be understood the circle of maximum diameter which is inscribable in said passage.

In the above mentioned mortar barrel the projectile is effectively guided by the parts in relief on the inner face, and the hollow parts situated therebetween form with the surface of the projectile outlets permitting the air contained in the barrel to be discharged during the loading of the weapon.

If desired the mortar barrel may at the discharge end thereof be provided With an extension having discharge apertures for the combustion gases and effecting the guiding of the projectile during the discharge of said gases.

In one application, an extension of this kind is an attached piece fastened to the barrel and provided with gas escape apertures.

According to another aspect of the invention there is provided a mortar projectile which on its side face has longitudinal projections extending over at least part of its length and determining its circular dimension gauge.

Depending on the applications, the projections, which slightly project beyond the circular dimension gauge of the projectile body proper, may be separated from tail ns, Iwhich may be provided to assist guidance, or else are made integral therewith. In one particular embodiment the projections are in the form of a squirrel cage composed of longitudinal ribs stilfened by perforated discs or rings.

The fact that the projections extend slightly beyond the gauge of the projectile body makes it possible to take up the clearance left between the body portion and the face of the barrel for the purpose of discharging air during the loading of the weapon.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l illustrates a mortar barrel having rectilinear grooves,

FIG. 2 is a partial view in section along the line II-II in FIG. l,

FIG. 3 is a variant of FIG. 1,

FIG. 4 illustrates a projectile according to the invention,

FIG. 5 is a variant of FIG. 4,

FIG. 6 illustrates a spindle-shaped projectile provided with slides similar to fins and used in combination with a grooved barrel,

FIG. 7 is another variant of the projectile according to the invention, and

FIGS. 8 and 9 illustrate modified forms of projectile.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, FIGS. 1 and 2, illustrate a mortar barrel 1 which has internal shallow rectilinear longitudinal grooves 2 which are rounded at the sharp corners. These grooves are advantageously of trapezoidal shape in order to prevent abrupt changes of section on the circumference of the barrel. The faces 3 form projections which are situated between the grooves and which form slides adapted to provide effective guiding for any projectile having an overall radius very slightly smaller than R (R being the radius of the barrel measured on the faces 3).

In the variant illustrated in FIG. 3`, the mortar barrel 4 is provided with internal helical grooves 5, which cover a part of said barrel and are continued on a projection 6 at the discharge end of the barrel and the projection 6 is laterally perforated by apertures 7, the rear portion 8 of the barrel near the breech being smooth. As can be seen from FIG. 3, the helical grooves 5 are situated partly in the region of and partly to the rear of the perforations 7. The helical form of the grooves 5 provides the advantage that the rectilinear fins of certain projectiles cannot penetrate therein and may be dimensioned to slide on the faces in relief between the grooves, thus enabling them to contribute towards the guiding of the projectile. The projection 6 may be a part attached to the discharge end of the barrel.

In FIG. 4, a projectile 9 according to the invention is provided with projections 10 disposed on its body portion and with tail fins 11. As the projections 10 and iins 11 have the same circular dimension gauge, they form an assembly of slides in two parts.

According to the variant illustrated in FIG. 5, the projectile 12 is provided at its tail with a guide drum in the form of a squirrel cage, composed of longitudinal ribs '13 braced by rings 14, their overall diameter being greater than the maximum diameter of the projectile body.

As shown in FIG. 6, a spindle-shaped projectile 15 slides by its body portion, and by tail projections 16 in the form of fins, on the faces 17 which are in relief and are helical in form and which are provided inside a mortar barrel 18.

The projectile 19 illustrated in FIG. 7 is provided with longitudinal projections or ribs 20 which have a rectilinear face 21 and are disposed on its body portion and which serve as guide slides. If desired, the tail fins 22 have the same overall diameter as the projections 20 and with them form an assembly of slides in two portions.

According to FIG. 8, a spindle-shaped projectile 23, of which the body portion 24 is curved, is provided on that portion with slides which form an integral part of the casing of the projectile body and which are formed by making grooves 25 in the face of the casing. The slides thus produced are of curved shape on their outer face, are not sufficient by themselves to effect the centering of the projectile, and are therefore assisted by tail fins 26 forming slides.

The projectile 27 in FIG. 9 is a variant of the projectile 23, differing therefrom by its body portion 28, lwhich is of cylindrical shape. The projections therefore have a rectilinear edge and by themselves are capable of effecting the guiding of the projectile.

By way of example, the hollows between projections may have a total cross-section amounting to 'between 1% and 3% of the cross-section of the bore of the mortar barrel, and a depth between 0.2 and 2 mm.

The devices according to the invention, which are adapted to provide effective guiding of the projectile, particularly during the critical phase of the blowing of the combustion gases, enable the projectile to be loaded in any position in relation to its axis and provided with such guidance without rotation with a gyroscopic effect.

In a combination of mortar and projectile according to the invention, achieved with a projectile the circular dimension gauge of which is inscribed in the inside face of the mortar barrel, the barrel and projectile come mutually into sliding contact in order to effect the guiding of the projectile, while forming discharge outlets for the air tending to be imprisoned between the projectile and the breech.

The combination of sliding contact faces and air escape outlets makes it possible to provide between said faces just sufcient clearance to permit the sliding of the projectile in the barrel and the effective guiding of said projectile, without hindering its downward travel in the barrel. The clearance thus left naturally depends on specific cases, and may be selected as desired Without affecting the loading of the weapon, that is to say the discharge of air.

In a device according to the invention the projectile is therefore guided positively during its movement in the barrel by contact faces forming slides. Two neighbouring slides are separated by a hollow, groove, or notch, the purpose of which is to permit the escape of the air imprisoned behind the projectile.

In various examples of construction of this device the slides are provided inside the barrel and form an integral part of the latter, while the projectile is smooth, or else the slides form part of the projectile While the barrel has a smooth inside profile; alternatively, a barrel having slides on its inside surface is used in conjunction with a projectile likewise provided with slides.

When the cylindrical inside surface of the barrel is grooved, the grooves have an adequate cross-section to permit the escape of the imprisoned air. These grooves are longitudinal or helical or similar, and the parts in relief left between these grooves constitute slides on which the projectile is supported. The grooves extend at least to the portion of the barrel where the compression of the imprisoned air would resist the downward movement of the projectile. It is not necessary for them to extend as far as the muzzle of the weapon or, in the direction of the bottom of the barrel, beyond the position occupied by the body portion, or portion of maximum cross-section, of the projectile on loading. The direction of the grooves may be selected as desired. Their width and number, the width of the slides, and in the case of helicoidal grooves the pitch of the helix will be so selected that, for example, any longitudinal rib or n which may be formed on the projectile is supported on at least one slide. The profile of the grooves will advantageously be amply rounded at the corners in order not to present a sharp angle to the sliding parts, and the same is done at the botto-m of the groove where a sharp angle would cause a concentration of stresses in the barrel wall. Thus, the parts in relief between the grooves constitute straight, helicoidal, or other slides which positively guide the projectile and resist its random movements.

It is advantageous for the total cross sectional area of the grooves (i.e. the cross-sectional area between the grooved prole and the original'ungrooved circular prole of the barrel) not to be too large, which would unnecessarily weaken the barrel, or too small in order not to retard the downward movement of the projectile excessively; in one embodiment this surface amounts to about l to 3% of the transversal surface of the bore. The depth of the grooves will depend on their width in relation to that of the slides, the caliber, etc. By Way of example, for a caliber of mm. and grooves and slides of equal width, a depth of from 2 to 0.2 mm. is adequate.

According to another application, the barrel has a front extension the inside face of which is adapted to come into sliding contact with the projectile and to guide it positively, while the combustion gases escape through holes provided at the bottom of grooves. An extension having a smooth or grooved inside face is capable of being used either with a smooth projectile or with a projectile provided with projections forming slides.

If desired, a barrel and its extension may both have slides, which may be of the same shape or else of different shapes. Depending on applications, these slides are independent or else are integral with one another in order to provide a single guide device extending through at least part of the barrel proper and also its extension.

In a variant of this last application, some of the slides (for example one out of two) are omitted in the extension, so as to obtain numerous narrow grooves in the barrel and wider but fewer grooves in the extension.

As mentioned above, another embodiment comprises projections or slides forming part of the projectile, while the barrel may be smooth. These slides are inscribed in a circle of a daimeter very close to that of the barrel, and slightly greater than that of the ventral portion of the projectile. When the slides are provided on the body portion, the diameter of that portion is equal to the diameter measured at the bottom of the grooves, furrows, or hollows between said slides.

Depending on applications, the `slides are formed in one piece or are composed of a plurality of parts or lengths. Their shape will depend essentially on the shape of the projectile. In an example applicable to a spindleshaped projectile, the slides are long and slender and extend over a large portion of the rear half of the spindle, and may be supplemented by short slides near the ventral portion of the projectile. Likewise by way of example, for a projectile composed of a body provided with a finned tail, the ns constitute a rear portion of the slides, while a front portion is formed in the ventral region by projections provided in the material of which the projectile casing is composed. Still by way of example, for a projectile designed to travel over its trajectory namely under supersonic conditions and consequently not provided with a reduced rear portion, the slides constitute an apertured drum extending the projectile, while the interior of the drum may if desired accommodate the firing charge.

In all these examples, the circular gauge enveloping the slides, which is lower than and very substantially equal to the passage gauge of the barrel, is slightly larger than the maximum transversal dimension of the projectile, so that the hollows between slides form air discharge channels or outlets by co-operation with the surface of the projectile body and the inside face of the barrel, which may or may not be smooth.

The barrel and projectile according to the invention may likewise be used in combination. Among many numerous arrangements they make it possible to obtain the following combinations, which are quoted by way of example:

Combination of a grooved barrel in its median portion (which is optionally provided with a front extension) and a projectile having the form of a spindle, the rear portion of which is provided with short slides similar to fins;

Combination of a barrel which is smooth in its median portion and provided with slides in a front extension and a projectile having slides at least near its body portion.

I claim:

1. A muzzle loading mortar barrel having a cylindrical inner face comprising a length portion provided with elongated grooves and a smooth length portion located at the muzzle end of the barrel, said smooth portion and the inner face lands between said grooves dening one circular gauge passage of uniform diameter.

2. A muzzle loading mortar barrel according to claim 1 wherein said inner face further comprises at the breech end of the barrel a smooth length portion of the same diameter as the muzzle end smooth portion.

3. A muzzle loading mortar barrel having a cylindrical inner face comprising a length portion provided with elongated grooves and a smooth length portion located at the muzzle end of the barrel, said smooth portion and the inner face lands between said grooves defining one circular gauge passage of uniform diameter, the wall of the barrel having through-perforations located at the bottoms of said grooves.

4. A muzzle loading mortar barrel according to claim 3 wherein said inner face further comprises at the breech end of the barrel a smooth length portion of the same diameter as the muzzle end smooth portion.

5. A muzzle loading mortar barrel according to claim 1, wherein the aggregate cross sectional area of the grooves is between 1% and 3% of the cross sectional area of said circular gauge passage.

6. A muzzle loading mortar barrel according to claim 1, wherein the depth of said grooves is between 0.2 and 2 mm.

7. A muzzle loading mortar barrel having a cylindrical inner face comprising a length portion provided with elongated grooves substantially inclined relatively to the barrel axis and a smooth length portion located at the breech end of the barrel wherein said smooth portion and the inner face lands between said grooves dene one circular gauge passage of'uniform diameter, wherein the aggregate cross sectional area of the grooves is between l%-3% of the cross sectional area of said circular gauge passage.

8. A muzzle loading barrel according to claim 2, wherein the aggregate cross sectional area of the grooves is between l%-3% of the cross sectional area of said circular gauge passage.

9. A muzzle loading barrel according to claim 3, wherein the aggregate cross sectional area of the grooves is between 1%*3% of the cross sectional area of said circular gauge passage.

10. A muzzle loading barrel according to claim 4, wherein the aggregate cross sectional area of the grooves is between 1%-3% of the cross sectional area of said circular gauge passage.

References Cited UNITED STATES PATENTS 37,924 3/1863 Steece. 460,102 9/ 1891 Carver 42-78 785,972 3/1905 McClean. 786,230 3/1905 McClean. 2,325,560 7/1943 Wauters 89-14 X 3,100,358 8/ 1963 Robinson 42-78 FOREIGN PATENTS 28,934 5/ 1925 France. 233,824 5/ 1925 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner S. C. BENTLEY, Assistant Examiner 

